1. Field of the Invention
This invention relates to an adapter for a flash illuminating device, and more particularly to an adapter for rendering a versatile flash illuminating device into an exclusive flash illuminating device suitable for use with various cameras.
2. Description of the Prior Art
What is known as the flash illuminating device has heretofore been called a strobo, which contains a boosting circuit, a main capacitor, a xenon tube, etc. and is caused to emit light by the tuning contact of a camera. In this case, on the camera side, the exposure information suitable for flash illumination photography, for example, the shutter time, is set to 1/90 sec. so that any malfunctioning such as slit exposure does not occur, and where the strobo is a light adjusting strobo, the operation of setting the aperture to an aperture value designated by the strobo is required prior to photography.
However, one is often apt to forget to set the shutter time and the like each time the flash illumination photography is to be carried out and if one forgets to set the shutter time and the like, one cannot obtain desirable photographs because the exposure is wrong. To eliminate such a disadvantage, there have been proposed various systems whereby the exposure value such as the shutter time may be automatically set when a flash-bulb flash device is set at its position for use (see, for example, German Pat. No. 1262765, U.S. Pat. No. 3,318,215, and U.S. Pat. No. 3,344,724). Particularly, in the case of a strobo, even if it is mounted to a camera, it will not emit light when the main capacitor is not charged to a level higher than its light-emitting level and for this reason, cameras in which the camera's shutter time is automatically set to a value suitable for flash photography only by closing a main switch have become commercially available. Further, there has been proposed a camera in which the shutter time or the aperture value is automatically set to a value suitable for flash photography only when the main switch is closed and the charge of the main capacitor reaches a predetermined amount (see U.S. Pat. No. 4,047,194), and various cameras of such type have become commercially available. When such camera is used, an electrical signal representing the closing of the main switch or the completion of the charging of the main capacitor is received from the strobo and automatically changed over into the shutter time or the like and therefore, the strobo usable with such camera must be an exclusive strobo suited for such camera. However, when photography is to be effected by using a versatile camera as well, it becomes necessary to prepare a versatile strobo (an ordinary strobo usable with other cameras than the exclusive camera) in addition to the exclusive strobo and this means a large scale of equipment. Also, where the quantity of light provided by the exclusive strobo is insufficient for the intended purpose, it is often the case that even if one has a versatile flash illuminating device having a great quantity of light, one cannot use such device with the exclusive camera and thus, one cannot fully effectively master various versatile strobos even if one has them on hand.
The commercially available exclusive strobos are provided with terminals positioned so as to correspond with the mounting portion of a camera, namely, the electrode on the accessory shoe, but the spacing between the terminals differs from one exclusive strobo to another and therefore, one must buy respective exclusive strobos for exclusive cameras. Also, an exclusive strobo is provided with a basic construction as a strobo, namely, a xenon tube, a main capacitor, a boosting circuit, etc., so that it may have the function as a strobo and therefore, when a versatile strobo is jointly used as described above, one must necessarily carry a weighty equipment because the versatile strobo also has the same basic construction as the exclusive strobo.
Also, there is a disadvantage that those who already have versatile strobos cannot use such strobos because such strobos are not at all usable with exclusive cameras.
As described above, the conventional versatile strobos are entirely useless for exclusive cameras and one must prepare a strobo suited for each individual camera and moreover, the conventional versatile strobos suffer from various problems in operability and portability.
Also, in these gears, the light adjusting type flash illuminating devices in which the reflected light from an object is metered so that the quantity of light emitted is automatically controlled in accordance with the metered quantity of light have come to be widely used because of their good operability. Such light adjusting type illuminating devices must be used with the camera's aperture device set to an aperture value designated to provide a proper exposure. With such devices, it is also possible to vary the light adjusting level in accordance with the object distance, but the designated aperture value is caused to assume a different value by varying the light adjusting level and therefore, the camera's aperture device must be re-set each time the light adjusting level is set. Also, as already described, even if the camera's shutter is of the focal type or the lens shutter type, it is necessary to set the shutter speed to a predetermined value in order to prevent slit exposure or to match the flash characteristic.
So, a flash system in which the setting of such designated aperture information and shutter speed is automatized to eliminate manual operation has been proposed, for example, in German Patent Publication No. 2703617 (published on Aug. 4, 1977 and corresponding to U.S. Pat. No. 4,047,194). This system requires four electrodes--the earth electrode, the synchronizing signal electrode for forming the transmission path of the trigger signal for triggering the discharge tube of the flash device, the photography mode change-over signal electrode forming the transmission path of the change-over signal for changing over the shutter speed control circuit or the aperture control circuit so as to be suited for flash photography, and the designated aperture signal electrode forming the transmission path of the designated aperture information--to be provided on both of the camera and the flash device and this has led to the complicated construction of the respective mounting members and in addition, when such flash device is used with a camera which does not have an aperture control circuit responsive to the designated aperture signal or a shutter speed control circuit responsive to the mode change-over signal, the designated aperture signal setting circuit or the photography mode change-over signal generating circuit provided in the flash device becomes useless and further, the flash device has been disadvantageous in that it is bulky and heavy because it contains such aperture signal setting circuit and photography mode change-over signal generating circuit.
Adapter devices adapted to be connected between a flash illuminating device and a camera to provide for various functions during flash photography are known. Most of them are for making the number or position of the terminals on the flash device side match the number or position of the terminals on the camera side, and simply transmit a tuning light emission signal from the camera side to the flash device side.
Also, an adapter device containing therein a display element for enabling it to be recognized on the camera side that the flash device has completed its light adjusting operation has been proposed (see, for example, U.S. Pat. No. 3,846,806). Further, an adapter device which enables it to be recognized on the camera side that the flash device has become ready to emit light has been proposed (see, for example, DAS No. 2149223). Still further, an adapter which, when the flash illuminating device has become ready to emit light, delivers guide number information to provide matching between the camera's terminal for operating the distance resistance input set on the camera side and the terminal of the flash device has been proposed (see, for example, U.S. Pat. No. 4,095,242). As will hereinafter be described, any of these adapter devices entirely differs from an adapter device which may be used with a versatile flash illuminating device, particularly, a light adjusting type electronic flash device, to receive, from the flash device, an exposure value control signal, namely, a mode change-over signal, for an exclusive camera and form a signal for adjusting the camera's exposure control device to a designated aperture value or a shutter time value providing a proper exposure for light adjusting flash photography, and there is known no adapter device constructed so that when the light adjusting level is varied, the change-over signal itself is varied.